anaerobic digestion thesis

7/29/2019 Anaerobic digestion Thesis

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THESIS RESEARCH REPORT

IN FULFILMENT OF THE AWARD OF M.Sc CHEMICAL ENGINEERING

(ENVIRONMENTAL ENGINEERING)

13/09/2007

SUPERVISOR: Dr. ILONA SARVARI HORVATH


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TABLE OF CONTENTS. Pgs

Acknowledgement..i

Dedication..ii

Abstract..iii

Chapter I.INTRODUCTION..1

-1.0.Introduction..............2

-1.1.Background Information.....2-3

-1.1.2.Basic Principles of Biofuels..3-3

-1.2. Biofuels Environmental Impacts .....4-5

-1.3. Biofuels Types......5-7

-1.3.1.Ethanol...5-5

-1.3.2.Biodiesel.6-6

-1.3.3.Non-food Biofuels..7-7

-2.1. Biogas ....7-8

-2.1.1.Key Drivers for Biogas Production....9-9-2.1.2.Biogas Prospects, Beneficiaries and Actors....9-9

-2.1.3.Resource Development and Waste Management10-10

-2.2. Process of Anaerobic Digestion..10-11

-2.3. Anaerobic Treatment Applications..11-12

-3.1. The Biorefinery Integrated Concept of Ethanol and Biogas....12-14

-3.2. European Legislation and Policy on Biogas.14-15

-3.3. Swedish Bioenergy Approaches.. 16-16

-4.0. Integrated Ethanol-Biogas Chart Flow.17-19

-4.1. Ethanol Distillery Waste- Stillage19-19

-4.2. Stillage Characterization . ........20-21


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Chapter II. AIMS AND METHODOLOGY.....22-22

-2.0. Research Objectives23-23

-2.1.Standard Method for Total Solids Analysis of Stillage Samples..................23-23

-2.1.2.Test Principle...24-24

-2.1.3.Equipment and Apparatus....24-24

-2.2. Standard Convection Oven Drying Procedure for

Total Solids TS% Stillage Samples24-24

-2.2.1.Precision..25-25

-2.3. Standard Methods for Volatile Solids Analysis of Stillage Samples......25-25

-2.4. Thermophilic and Mesophilic Anaerobic Digestion of

Ethanol Distillery Stillage.......................................................................................26-26

-2.4.1.Introduction...26-26

-2.4.2.Materials and Supplies......27-27

-2.4.2.1.Equipment and Apparatus..........................................................................28-28

-2.4.3.Samples, Reagents and Supplies...28-28

-2.5. Method..27-27

-2.5.1.Laboratory Experimental Procedures....28-29

-2.5.2.Experimental Consistency and Monitoring...29-29

Chapter III.RESULTS...30-30

-3.1. Data analyses and Presentations....31-32

-3.1.1.Total Solids (TS) and Volatile Solids Computations of Stillage....31-32

-3.2. Anaerobic Digestion of Ethanol Distillery Stillage Samples.....33-34

-3.2.1.Mesophilic Anaerobic Digestion of Wheat Stillage35-35

-3.2.2.Mesophilic Anaerobic Digestion of Lignocellulose Stillage...36-36

-3.2.3.Comparison of Wheat Stillage and Lignocellulose Stillage....37-37

-3.3. Thermophilic Anaerobic Digestion of Wheat Stillage. ......38-38

-3.3.1.Thermophilic Anaerobic Digestion of Lignocellulose Stillage.......39-39


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Fig.4.Pathways of Biofuel Production...7-7

Fig.5.Biogas Drivers.....9-9

Fig.6.Biogas sustainable Benefits.....10-10

Fig.7.Schematic illustration of Anaerobic Digestion for Biogas Synthesis.....11-11

Fig.8.Integration of Anaerobic Digestion and Waste Recovery......12-12

Fig.9a&9b.Swedish Biofuel Progressive Report.....16-16

Fig.10.Evaluation of Swedish Biogas Plants Upgrading.....17-17

Fig.11.Conversion of Lignocellulose Biomass to Ethanol.......18-18

Fig.12.World Fuel Ethanol....21-21

Fig.13.European Ethanol Production Statistics..21-21

Chapter II.AIMS AND METHODOLOGY

Fig.14.Experimental set up for Methane potential yield measurement for

Mesophilic and Thermophilic Anaerobic Digestion....28-28

Fig.15.Triplicate curve averages for Methane yield from

Wheat Stillage at 35C.....35-35

Fig.16. Triplicate curve averages for Methane yield from

Lignocellulose Stillage at 35C....36-36

Fig.17.Methane Potential Triplicate Average Composition curves of

Lignocellulose Stillage and Wheat Stillage at 35C....37-37

Fig.18.Methane Potential Triplicate Average Composition curves of

Wheat Stillage at 55C.....38-38

Fig.19. Methane Potential Triplicate Average Composition curves of

Lignocellulose Stillage at 55C....39-39

Fig.20. Methane Potential Triplicate Average Composition curves of

Lignocellulose Stillage and Wheat Stillage at 55C....40-40

Fig.21A. Methane Triplicate Average curves for respective samples at 55C

(Thermophilic Digestion).....41-41


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Fig.21B. Methane Triplicate Average curves for respective samples at 35C

(Mesophilic Digestion)...41-41

Fig.22. World Ethanol Production..53-53

ABBREVIATIONS USED

WSWheat Stillage

LS.Lignocellulose Stillage

Rf.Reference Avicel Sample

CSControl Samples

VSVolatile Solids

TSTotal Solids

TPTotal Protein

TF.Total Fat

Vete..Wheat

EnhetPercentage

CO2(g)

...Carbon (IV) Oxide gas

N2(g)..Nitrogen gas

CH4(g)Methane gas.

std.Standard

nnumber of moles

RIdeal Gas Constant

P(atm)..Atmospheric Pressure

TTemperature

KKelvin (Standard Temperature unit)

V....Volume (L, m3).

OFMSW.Organic Fraction of Municipal Solid Waste


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ACKNOWLEDGEMENT.

The research work for this thesis was carried out at University College of Bors School ofEngineering Sweden within a six month intensive rigorous practical explorations. This thesiswith its fragile nature would not have been finalized without supervision, assistance and

professional support and encouragement of unique personalities. I would like to acknowledgepriceless positive and constructive supervision of Dr. Ilona Horvath Mrs., the SwedishEthanol producing company, Agroetanol for the provision of the Feedstocks utilized for theconduction of the project thesis as well as the personnel of the Environmental EngineeringDepartment, University College of Bors and also many thanks to ESPIRA, the Research

project awarding body for the award honor granted to me for my Research Thesis as the BestMost Promising Commercially Research Project as promising roadmap for FutureSustainability.

My profound appreciation to Dr. Dag Henriksson, the Director of Studies and Head ofDepartment of Environmental Engineering University College of Bors for his outstanding

immeasurable professional effort in this thesis. Special humble thanks to Michael Tittus,Associate Professor Anders Nylund and Professor Hkan Torstesson for your wonderfulremarkable impacts.

Special heart warm thanks to the Mr. & Mrs. Gustafson, Dr. & Mrs. Henriksson and Mr.Kwame Aboh for their huge unparalleled and unquantifiable outstanding support andfinancial assistance towards the successful completion of my studies. Vote of thanks to theAdvent Church Members Bors, my wonderful friends and colleagues (Wiktor, Marion,Anastasia and Maskim, Vinnay Reddy, Charlotte, Jenny, Emma Nilsson, Emma Karlsson,Tayo Lekuti, Edwin, Shedrack, Nelly, Richard and Lilli, Alinda, Mohamed, Bada, Zahra,Zhoreh, Shanin and others) for their assistance and labor of love.

Most profound gratitude to my Loving and Caring Parents, Barrister & Mrs. ChristopherOladunni Awosolu, sweet wonderful Siblings (Dr. Samuel Awosolu, Dr. Gabriel Awosoluand Mrs. Olutoye Joshua) and Micheal Adewole Ologbenla for your loving kind gesture,genuine support, care and encouragement. Thank you so much youre very wonderful treasureand unique Loving Family.

Above all, I give Almighty God the Glory, Honor, Thanks and Praise for His Presence, Love,sustenance, and grace for the successful completion of my studies. Thank you God for makingthis Research project a unique achievement with promising future prospects.

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DEDICATION.

In Evergreen Loving Memory of my Dearly Beloved Brother, Emmanuel Olusegun Awosolu.

Youre a Rare Gem gone too soon, I will never forget your esteem love and care you nurtured

me, I really dearly miss you very much. May your Gentle Soul Continue to Rest in PerfectEternal Peace in Bosom of the Lord, Amen Adieu.

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Abstract

iii

Dependence on oil imported from foreign countries affect the National Energy securities

and Energy security of global economies has become one of the most challenging problem

that needs to be resolved as the fossil sources are fast diminishing and irreplaceable. The

alarming energy demand and consumption rate of the present global status is currently

exponentially exceeding the rate of local supply sources, becoming an issue of concern. A

look beyond the fossils is crucial for long tern economic growth and energy security as

there are numerous uncertainties about the fossil supplies coupled with the greater

environmental risks encountered during exploitation. Thus the new concept for treating

ethanol distillery waste anaerobically to produce Biogas- a clean renewable alternative

energy with many applications projects sustainable and more realistic option.

The research project focuses on Comparison of the Potentials and Efficacy of Anaerobic

Digestion of Stillage (Wheat Stillage and Lignocellulose Stillage) from Ethanol Distillery

plants for Biogas Production. It also investigates better alternative temperature dependent

Stillage Anaerobic Digestion that will enhance a higher Biogas yield.

Anaerobic digestions were performed in triplicate batch systems, during both mesophilic

(35 C) and thermophilic (55 C) conditions at a period of 50-days. The reactors contained2.73g of Wheat Stillage and 5.2g of Lignocellulose Stillage samples, respectively,

corresponding to 2% VS in each reactor. The inoculum was taken from either a mesophilic

Biogas Plant (Gsslosa., Bors), or from a thermophilic Biogas Plant (Sobacken, Bors). A

Gas Chromatographic method (GC) was employed for determination of the obtained biogas

composition.

The theoretical CH4 Potential for Wheat Stillage and Lignocellulose Stillage is 0.473

m3CH4/kg VS and 0.407 m3CH4/kg VS, respectively. The results obtained from this study

indicated, however, that the Wheat Stillage performed better under thermophilic conditionswith a peak of 575ml CH4 / 0.5g VS; while the Lignocellulosic Stillage gave the best

performance under mesophilic conditions leading to a methane production of 436ml CH4/

0.5g VS after 4 weeks of digestion period.


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1.

I. INTRODUCTION


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1. Introduction.

1.1 Background Information.

Oil prices are at all times high and there is growing zest to reduce our dependence on oil. It isfinite resource, gas supplies and oil reserves are shrinking, will definitely run out in the future.

World energy demand is expected to double by 2050 as it is shown in fig 1 below. The

demand of energy is currently exponentially exceeding the rate of local supply sources, a look

beyond the fossils is crucial for long term economic growth and energy security purpose. The

volatile situations in the Middle East, where vast reservoirs are, are also creating uncertainties

about the availability of the supply. There is also the greater environmental risks associated

with exploitation of crude oil.

Fig.1. Illustration of Projected World Energy Demand.

Dependence on oil imports, affect the national energy security of any country. Energy

security of global economies has become one of the most challenging problems that need tobe resolved. Energy is crucial for development hence living standards, in order to sustain and

improve living standard it will be very important to avoid any energy crises. This can only be

achieved through the development of new technologies or modification of existing ones.

There is also the need to continuously develop alternative energies.

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Fig.2. Associated Consequences of Imported Oil Dependence: Calstat Data, June 2005.

For Sustainable energy supply, efficient and diverse energy resources are important both for

short term and long term utilizations. It is however important and safe precautionary measure

to develop renewable alternative energies and more realistic increasing their use, taking into

consideration the present and future consumption of energy, capital investments, issues of

renewability and pollution reduction. It is therefore imperative that these alternative

renewable energies are cheap, safe to produce and use, and are continuously available. It

should be noted that any investment in alternative energy today will yield high profits

tomorrow and that investment must start now.

1.1.2 Basic Principles of Biofuels.

Unlike fossil fuels, biofuels are bio-based from biodegradable portion of municipal wastes,

forestry and agricultural energy crops. Biofuels are renewable and environmentally friendly

alternative energies as compared to non-renewable fossil fuels that elicit green house gas

effect.

Biofuels are currently embracing public interests as supplement to oil based to serve astransportation or automobile fuels and also sources of heat and electricity generation supplies.

Upon combustion, Biofuels reduce net emissions of Carbon (IV) oxide with other associated

green gases attributed to global environmental climatic changes.

There are various types of Biofuels with marked differences and similarities in technological

processes which can either be in liquid or gas form with each having specific attributes

determining the final usage and specified end products.

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Biomass- general use.

As illustrated in the fig.3a and fig.3b below, Biomass can be utilized for different applications

such as Synthesis of Chemicals and Pharmaceuticals, production of animal feeds or food,

generation of energy or fuels and manufacture of construction materials. The Energy

utilization can be derivative from various processes such as anaerobic digestion, ethanol

fermentation gasification, combustion shown in the fig.3b below.

Fig.3a. Illustration of Biomass utilization. Adapted from Institut Umwelt-Sicherheits, EnergitenikUMSICHT

Fig.3b. Illustration of Biomass and Energy Use

4.

Adapted from


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1.2. Biofuels Environmental Impacts.

The environmental quality has been largely affected as a result of petroleum based

transportation fuels use and production with significant consequence on urban air pollution.

The detrimental consequences of the fossil based fuels and the depleting supplies of

petroleum have prompted and triggered the search for renewable transport fuels such as

Biofuels. To be justified sustainable as alternative, biofuelshould meet peculiar criteria such

as providing a net energy gain, positive favorable environmental effect and benefits,be

economically cost effective and competitive, with large production capacities without

hindering food supplies.

Summarily, peculiar interesting features of Biofuels are

The substrate basically wastes including wastes from municipalities and such helps in

Environmental Clean up.

Relatively produces lower CO2(g) emissions compared to fossil fuels

Biomass derived, readily available, cheap and renewable with foreign independence

importation prospects

Do not contribute to environmental pollution.

1.3. Biofuel Types.

These Biofuels are derivatives of food crops, agricultural residues, waste from municipalities

and industrial waste. Principal commercial types of the first generation biofuels are

Bioethanol and Biodiesel.

Ethanol and Biodiesel appear to be thriving into a new market promotions caused bycombination of factors of the increase in petroleum prices and new energy policies and

regulations.

1.3.1. Ethanol

Ethanol, a distilled colorless liquid fuel obtained from numerous potential feedstock varieties

such as sugar beet, wheat, corn, cassava, fruits, baggasse, barley, molasses, skim milk (whey),

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potatoes, sorghum, switch grass and cellulose biomass such as wood, paper, straw and other

cellulose wastes such as grasses, others includes municipal solid wastes. These various waste

streams for Ethanol production have their peculiar properties and generally differ. Feedstocks

prices and price of natural gas are predominant influential factors that determine the cost of

Ethanol Production. Ethanol as an alternative fuel, offers a Sustainable economy by reducing

the use of imported petroleum, emitting neutral CO2(g), boost economy providing value added

market opportunities for the Agricultural sector (Shell Global, 2001).

Ethanol with its high octane count has is currently positively used as an automobile fuels with

policies to promote its production most especially in Brazil, United States, majority of the

European Union Countries and South Africa.

1.3.2. Biodiesel.

Biodiesel is mainly produced from animal fats and vegetable oil sources. This is a methyl or

ethyl derived organic fuel from waste cooking oil or animal fats Either blended with

petroleum diesel at various ratios (80 percent petroleum diesel and 20 percent biodiesel) or in

its pure form (B100) is a dependable alternative to petroleum diesel. Primarily produced from

chemically catalyzed acid or base reaction between alcohol and vegetable oil can be used in

vehicles with engines specified for low blend concentrations or pure concentrations.Furthermore renewable agricultural sources such as vast vegetable oil and animal fats sources

comprise of Virgin Plant oils such as (rapeseed oil commonly used in Sweden and Europe,

Soybean, Canola oil, sunflower, saffleflower), Crude vegetable oils, greases, edible and non

edible tallow, used fried oils, acid oils can also be used for biodiesel production.

Summarily, Bio-based compared to Conventional Fossil fuels, environmentally friendly

renewable fuels and Waste Management options. (Shell Global, 2001). Ethanol and Biodiesel

have similar strengths in utilization of great variety of Feedstocks, Particulate emission

reduction, Oil independence, Stimulant to Farming Sector, Sustainable and Non-Toxic,

National Security, Global market expansion with job opportunities,

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1.3.3. Non-food Biofuels.

These Biofuels constitute the second generation of Biofuels and consists of straw and

woodchips. They substitute the use of food crops, so that the food crops can be solely for

consumption and avoid the shortage impacts on food crops. Significantly these non-food

biofuels could reduce CO2(g) emissions. (Shell Global, 2001)

Fig.4 Pathways for Biofuel Production (Shell and Codex 2006): The Biofuel Magazine.

2.1 Biogas.

Bacteria degradation of biological and organic matter in the absence of oxygen known as

Anaerobic Digestion generates Biogas. The Anaerobic digestion is an effective proven

technology for handling and treating biological wastes and effluents for generation of district

heating and electricity supplies, as well as clean environment. Depending on the feedstock,

Biogas is principally mixture of methane (CH4)g, Carbon dioxide (CO2)g and minute traces of

hydrogen sulphide (H2S)g, hydrogen, nitrogen, ammonia (NH3)g and sulfur dioxide (SO2)g .

Methane is the only constituent of Biogas with significant fuel value. The inert diluents of

Carbon dioxide (CO2)g and nitrogen lowers the calorific content of the gas, while hydrogen

sulphide (H2S)g, corrosive nature wears down the anaerobic digester and pipes involved in

the gas distribution.

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The process of anaerobic digestion is carried out in a simplified number of steps using any

substrate of organic or biological origin and occurs in septic tanks, rubbish dumps, garbage

refuse bins, decaying municipal waste or food waste.

The sources of Anaerobic Digestion can be classified specifically as either:

Agricultural materials such as liquid manure, energy crops and crop residues (Ley crops,

maize, straw, sugar beet), Silages (grass silage, maize silage), Vegetable wastes

Industrial residues such as Distillery wastes (Stillage), Whey, and Pomace.

Municipal wastes such as Source Separated Solid Organic Wastes.

Municipal wastewaters and Sewage Treatment Plants

Animal manures and Slaughtery wastes. (O. Jnsson, ENGVA 2001, Malm)

Methane potential fraction differs and ranges between 40%-80% do the basis of the digester

type, substrate quality and digesting bacteria (Stewart et al., 1984). A small fraction of

hydrogen sulphide often is present in Biogas (Speece, 1996).

In Table.1 below the varying percentage constituents of Biogas according to (Stewart et al.,

1984) is shown

Constituents % Composition

Methane 50-75

Nitrogen 0-1

Carbon IV Oxide 30-45

Water 0-1

Ammonia Traces

Hydrogen Sulphide Traces (ppm)

Table.1. Varying composition of Biogas components mixture. (Stewart et al., 1984).

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2.1.1 Key Drivers for Biogas Production.

Fig.5 highlights the major influential key factors for search of alternative renewable fuel,

Biogas are

Oil Independence,

Reduced Emissions,

Rural Development and Value Added Agriculture

Fig.5. Biogas Drivers

2.1.2 Biogas, Prospects, Beneficiaries and Actors

- Potential Beneficiaries & Policy Actors

Municipalities and Industrial Authorities

Solid Waste and Waste-water treatment Sectors

Energy and Transportation Industries

-Future Prospects

Business Development Opportunities: Long-term investment in infrastructure, financial

incentives, extensive biogas supply and an integrated approach are keys to ensuring stable

market conditions and large- scale public buy-in of biogas fuelled transport and digestates

returned to farmers as valuable fertilizers, this however involves technological innovations

and consistent upgrading of utilization of available resources.

Socio-Economic Development Opportunities: The cost-benefit analyses of methane

generation vary widely, depending upon the uses and actual benefits of biogas production,

public and private costs associated with the development and utilization of methane and on

the technology used to generate methane. It promotes sustainable Agriculture, an economy

wealth to the rural areas with addition increased economic investment returns.

9.

KEY DRIVERSGLOBAL

WARMING

AIRENERGY

B

I

O

G

A

S


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2.1.3. Resource Development and Waste Management

In fig.6 below represents the prospective promising benefits of Biogas Utilization, basically

Biogas Production redirects drifts of potential waste streams from landfills to more cost

effective reusable energy essential for the transport and municipal industries.

It offers a lasting solution and applications for Waste Management and Resource

Development requirements for the achievement of the three basic needs of the society.

ENVIRONMENTAL HEALTH

SUSTAINABLE COMMUNITY

ECONOMIC PROFITABILITY

NATIONAL SECURITY

Fig.6. Biogas Promising Sustainable Benefits

2.2 Process of Anaerobic Digestion.

Biogas Production through anaerobic digestion is a biochemical process involving microbial

flora of bacteria adapted to oxygen free environment to convert complex biological andorganic wastes in sequential stages into Methane, the major energy fuel.

Anaerobic digestion process is continuously undergoing modifications with improvement and

development of new and complex technologies which are rapidly emerging. The anaerobic

digestion process is temperature influenced and dependent. Some of the anaerobic bacteria

have optimal degrading rate at mesophilic temperature of 32-35C range, while other

digesting bacteria have maximal potentials at thermophilic temperature range of 50-55C

range. These anaerobic bacteria flora are different in their functions at different stages of the

digestion and there are four digesting bacteria types.Fig.7 is a schematic illustration of the

three sequential stage processes of Anaerobic Digestion as explained briefly below.

The Hydrolytic Bacteria primarily are involved in the break down of complex organic

waste streams into simple sugars, fats and oils, and amino acids. This stage involves

splitting of the complex organic biological molecules into simpler forms, the process is

known as Hydrolysis or Liquefaction.10.

RESOURCE DEVELPOMENTWASTE MANAGEMENT


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The Fermentative Acidogenic Bacteria convert the hydrolyzed portion into Organic acids.The Fermentative Acetogenic Bacteria then convert the Organic acids into Hydrogen,

Acetate and CO2(g)

Finally, the Methane producing Bacteria, the Methanogens simultaneously produce

Biogas from the Acetate, or from Hydrogen and Carbon (IV) oxide.

Fig.7. Schematic illustrations of the Anaerobic Digestion Process for Biogas Synthesis

2.3. Anaerobic Treatment Applications.

Many European Communities are recently embracing the anaerobic digestion as waste

management treatment application following the strict Environmental regulations of

abatement of greenhouse gases.

Anaerobic Digestion technology is a proven energy yielding odor removal process applicable

in converting organic and biological content of waste Feedstocks into biogas and other

residual by products which can be further reprocessed for secondary applications.

11.

Organic

Wastes Methane

Methane

Post

TreatmentIndustrial, MunicipalAgricultural, Domestic

Sludge

Complex Organic Molecules

Monomers

Organic acids, Ketones, Alcohols

Acetate, CO2(g), H2(g)

Hydrolysis

Acidogenesis

Acetogenesis

Methane, CH4(g)Methanogenesis

Fermentative acetogenic bacteria

Methanogenic bacteria

Digestates

Fermentative acidogenic bacteria


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Unique in its features, anaerobic digestion not only mitigates pollution problems but also a

cost effective reliable technique solution for dependable fuel, electric and heat generations for

cleaner and healthier environments. According to Viswanath et al., 1992 in fig. 8 below

illustrates the integration of anaerobic digestion biomass based by-product and waste recovery

It redirects wastes from landfills such as organic municipal solid food waste from cafeterias

and restaurants (Bouallagui et al., 2003; Hans et al., 2005; Kiely et al., 1996) Crop residues

(Stewart et al., 1984; Weiland, 1993), liquid waste water from food processing plants

(Viswanath et al., 1992)

Fig.8. Integration of Anaerobic Digestion in biomass based by-product &waste recovery Viswanath etal., 1992

3.1 The Biorefinery Integrated Concept of Ethanol and Biogas.

Fermentation of agricultural Feedstocks for Ethanol Production is an established process. The

search for substitutions for fossil fuels is enhanced by the skyrocketing increase in oil price,

oil war provocation and growing concern neutrality concern of CO2(g). Ethanol Production

through the conversion of sugar, sugar beets or sugarcane, starch content of varieties of

biomass Feedstocks such as wheat and corn involves the utilization of Enzymes and heat

applications to break down the complex sugar into simple sugars that will further be

processed by the fermenting organisms; yeasts into Ethanol and distilled to fuel Ethanol.

The emerging application of cellulose biomass feedstock is relatively new process not yet

fully commercially large scale but with higher possibility of broader use on the basis of

abundant varieties and cost inexpensiveness as illustrated in Table.2 below.

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Feedstocks for Ethanol Production can be broadly classified as shown in the below.

Sugars Starches Cellulose

Sugar beets, Sugarcane Grain and Root Crops Wood, Crop Residues, Energy crops

Table 2. Primary Potential Feedstocks for Ethanol Production.

The sugars can be directly used for Ethanol Production since they are in the simplified form

required for Ethanol Production.

The Starch Feedstocks must be converted into the fermentable units through hydrolysis either

by enzymatic or chemical hydrolysis. The Cellulose waste streams essentially have to

undergone acid or enzymatic hydrolysis for ease of fermentation of the hydrolyzed sugars into

Ethanol. (Bayer Technology, 2001).

The cellulose waste stream often might be difficult in processing for ethanol production due

to the varying lignin content in the Feedstocks utilized and due to the formation of

fermentation inhibitors under the chemical hydrolysis step.

Four major steps are involved in the production of the distilled alternative fuel- Ethanol

Screening of harvested cultivated feedstock raw materials for viability

Pretreatment and Hydrolytic conversion of Feedstocks into fermentable substrate

Hydrolyzed Substrate Fermentation, Distillation and Purification

Bioconversion Treatment of Fermented Residues and Bio-recovery of End products.

It should be noted that following screening for viability production potential of the feedstock,

physical, chemical or biological pretreatment or combination of these must be done. (Hsu,

T.1996).

The Physical Pretreatments are generally size reduction and aqueous or stream processing.

The size reduction can either be ball milling, hammer milling or compression milling.

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Aqueous or steam pretreatment method is often acid or base catalyzed, the main objective of

this method is to process the feedstock biomass with hot water or steam applications at high

temperatures and pressures for short periods. In this process the use of acids and other

chemicals are minimized with high sugar recovery tendencies and minimal fermentation

inhibition.

Chemical Pretreatments use chemicals which can be acidic or alkaline solvents such as dilute

acid, ammonia and dilute alkaline solvents.

Biological Pretreatments are widely applicable for Cellulose feedstock digestion to solubilize

lignin and provide larger surface area for hydrolysis into fermentable sugars.

Combination of either of the Pretreatment methods may enhance the effective yield of

Ethanol Production. Combined pretreatments often result in separating components into

individual product streams as depicted by Technology adopted by Bayer involving an

Integration of Ethanol Production with the conversion of the Distillery waste product into

Biogas and its numerous application uses (Bayer Technology, 2001).

3.2 European Legislation and Policy on Biogas

The major objective of the European energy policy is to attain competitive, sustainable and

secure energy. Europe is increasingly becoming vulnerable to rising energy prices, climatic

change and to the unpredictable reserves of fossil fuel.

The ultimate key to attaining sustainable future depends on a drift to use of alternative

renewable energies. In reference to the adopted legislation, more than 20Mtoe estimated

deposit of organic waste as shown in Table.3, produced 4.7Mtoe of Biogas in the European

countries in 2005 with from municipal wastes, agricultural wastes, mainly from sewage

purification plants. This however significantly benefited biogas methanisation with 11.1%

production growth in the European primary energy between 2004 and 2005. (EurObserVER

2006).

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Summarily the European Union member States Biogas Legislations are:

To reduce green house emissions (Kyoto protocol 1997)

-Demand for renewable clean greenhouse gas emission-free fuels.

Increase in demand for energy-security energy supply

Promoting Environmental Sustainability

Promotion of biofuel for transport EU-Directive 2003, 2% Increase in 2005 to 5.75%

increase by 2010.

Projecting the European Economies Competitiveness.

Moreover the in the European States or the European countries there was marked noticeable

increase in Energy Production in kilotonnes as illustrated in Table.3 below between 2004-

2005).

Primary Production of Biogas (ktoe) in the European Union in 2004 and 2005.

Table 3. Source: EurObserVER 2006, European Commission on Energy EUROPA.

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Public Consumer Acceptance.Effective Waste Management Technologies and Services.

Proven Technologies and International Partnerships

4.0. Integrated Ethanol-Biogas Process:

Comparison of Starch Based Feedstocks and Lignocellulose Materials.

Swedish Bioenergy Concept of Integrated flow chart of Ethanol Plant and Biogas Plant.

Fig.10. Evaluation of Swedish plants Biogas Upgrading; M. Persson (2003).

Consequent on the rapid industrial developmental growth, there is urgent need for production

of sustainable energy sources. Following the premise of increasing demand of attractive

sustainable energy with environmental laws implementation in many countries, cheap

substrates and efficient ethanol production processes are essential.

Currently production processes of fuel ethanol involves utilization of crops such as corn,

sugarcane are well established, to be more competitive to fossil fuels, the utilization of

cheaper biomass or substrates such as Lignocellulose could be more promising although it has

many associated challenges of complex processing and substrate utilization that requires

efficient active microorganisms capable of withstanding stress conditions and fermenting

variety of sugars mainly (pentose and hexose).

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Ethanol production process can either be starch based or Lignocellulose based. The

production of ethanol from starch based biomass such as grains or cereals involves conversion

of the milled cereal or grain through a liquefaction stage to render the starch soluble and then

proceeded with a hydrolytic step into fermentable glucose. The glucose is further processed in

combination steps known as Simultaneous Saccharification and Fermentation involving

enzymatic hydrolysis and fermentation to produce Ethanol, CO2(g) with other residues as

depicted in Fig.10 above with schematic illustration of ethanol production from starch

biomass. Further purification processes during the Distillation and Dehydration processes are

to obtain pure fuel Ethanol which can also be blended with other fuel types such as petrol.

Lignocellulose biomass comprises of agricultural residues, paper wastes, wood, forest

residues and these biomass have their composition made up of Lignocellulose which consistsof three main biopolymers of hemicellulose, lignin and cellulose. The sugars found in

hemicellulose and in cellulose content having conversion potential into fuel ethanol by a

fermentation process.

However a major limiting factor is owing to the presence of several inhibitory compounds

coming up during the hydrolysis step, especially when chemical hydrolysis is used for

liberating the sugars.

Lignocellulose based Ethanol Production process involves primarily first conversion of the

size reduction and pretreatment of the Lignocellulose Biomass as illustrated in Fig.11.

Fig.11.Conversion of Lignocellulose Biomass to Ethanol: Trends in Biotechnology; Zacchi, G. (2006).

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Moreover, the pretreatment methods could be enzymatic, acid or alkaline pretreatment

methods. The enzymatic pretreatment amidst its limitations offers the most promising

pretreatment result. The hydrolysis of the cellulose and hemicellulose chains release the

repeating sugars which are then fermented by filamentous fungi, bacteria or yeasts

Although similar steps are involved but contrary to production of ethanol from starch biomass

there is need for Detoxification especially if Chemical hydrolysis methods are used before

Fermentation process in order to improve efficiency of the fermentation process and reduce

the Inhibitory concentration.

4.1. Ethanol Distillery Waste- Stillage.

One of the most polluting industries are the Alcohol distilleries, generating an average of 8-

15 L of Stillage effluent per liter of ethanol produced. (Saha et al., 2005). Stillage is a non

toxic biodegradable effluent which is the main source of pollution in distilleries. However,

Stillage treatment can also be energy recovery process to produce Biogas, which can be

obtained by anaerobic digestion of the Distillery waste- Stillage.

Qualities of Stillage differ following the various enormous feedstock sources applied for

Ethanol Product. Anaerobic digestion of Wheat Stillage is significantly different from other

Stillage obtained from molasses, fruits, potatoes, rice etc., higher protein contents and higher

saccharides of lower biodegradability account for the significant differences. (Miroslav et.al,

2005).

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4.2. Stillage Characterization

Parameters for the characterization of Thin Stillage sample, a distillery waste obtained as

byproduct of Ethanol Production are basically the Total Solid Contents (TS), Volatile Solids

Contents(VS), Total Suspended Solids (TSS), Volatile Suspended Solids (VSS), Total

Chemical Oxygen Demand (TCOD), Volatile Fatty Acid (VFA), Total Protein (TP),

Carbohydrates mainly the Sugar (Glucose) Contents, Ratio of the Chemical Oxygen Demand-

Volatile Solids COD/VS, Ratio of the Volatile Solids-Total Solids fractions (VS/TS), pH.

The IOWA Biotechnology Byproducts Consortium, 2005 characterized Thin Stillage into

respective chemical contents with varying composition as shown in Table 5.

20.

Parameters Thin Stillage Sample

% TS 6.1

% VS 5.3

VS/TS 0.87

%TSS, %VSS 2.1

TCOD g/L 94

COD/VS 49

pH 1.8

Carbohydrates mg/L (glucose) 13, 600

TP, mg/L 1,292

VFA, mg/L 4.46

Table 5. Characterization of Thin Stillage, Iowa Biotechnology Consortium; Samir et al., 2005


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Ethanol fuel production is increasing rapidly around the world as depicted in Fig.12 below,

Fig.12. World fuel Ethanol Production; Renewable Fuels Association, 2005.

As illustrated in Fig.13 below, the major fuel ethanol producers in the European States are

namely Sweden, Spain and France. France in the decades earlier, pioneered the European fuel

ethanol market position until lately in the late 19th century was Spain and presently progressive

ethanol production in Sweden.

Fig.13. European Ethanol Production Statistics; Renewable Fuels Association, 2005.

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II. AIMS AND METHODOLOGY

22.


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2. Research Objectives

The Research thesis primarily focuses on Biogas Potential of different Stillage Samples using

batch digestion under both Thermophilic conditions and Mesophilic conditions with focus on

comparison of the Potentials and Efficacy of Anaerobic Digestion of Stillage (Wheat Stillage

and Lignocellulose Stillage) from Ethanol Distillery plants for Biogas Production.

It also investigates comparison of temperature dependent Anaerobic Digestion processes

either Thermophilic Anaerobic Digestion or Mesophilic Anaerobic Digestion in determining a

better alternative temperature dependent Stillage Anaerobic Digestion that will enhance a

higher Biogas yield.

Distillery Ethanol By-Product Stillage samples from Swedish Ethanol producing plants(Agroetanol, Norrkpping and SECAB rnskldsviz were collected. The Stillage Samples

were stored at 4C. Based on the hygroscopic nature of the Stillage samples with high varying

percentage of moisture, for precision, the general chemical analyses were experimentally

conducted on dry weight.

The samples were characterized and analyzed for total solids TS (%), volatile solids VS (%),

Carbohydrate content (Sugar), total nitrogen TN (%) and total fat TF (%)based on standard

determination test methods for organic biomass samples. The total nitrogen and total fat

contents of the Stillage samples (Wheat and Lignocellulose), were performed at AK Lab

research institute. However, it should be noted that the characteristics of Stillage are highly

subjected to the feedstock and the dependent on the ethanol production process.

2.1. Standard Method for Total Solids Analysis of Stillage Samples.

Primarily based on the determination of the total solids contents, that is the sample residue leftin the crucible after evaporation of the Stillage samples (Wheat Stillage and Lignocellulose

Stillage) using National Renewable Laboratory Energy Standard Methods in a convection

oven at 105C. The Total Solid Content (%) is the amount of sample residues remaining

following heating the Stillage samples in a convection oven at a temperature of 105C

expressed in (%).

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2.1.2. Test Principle: A well mixed sample of each Stillage is evaporated in a weighed dish

and dried to a constant weight in a convection oven for overnight at a temperature of 105C,

the weighed samples are placed in the during the above specified time and dried until a

constant mass is obtainable.

2.1.3. Equipment and Apparatus:

Porcelain evaporating crucibles of approx. 90mm diameter,Analytical balance with sensitivity capable of weighing 0.01gDrying oven for operation at 103C-105C temperature

Desiccator

MicropipettesMagnetic StirrerMetal Tongs.2.2. Standard Convection Oven Drying Procedure for TS % Stillage Samples.

The Convection Oven Procedure based on the ASTM E1756-01 method by Department of

Energy, the National Renewable Energy Laboratory (NREL) 2005, USA was adopted in this

standard test determination method for the Stillage samples to be analyzed as it is easy to use,

precise, relatively cheap test method, widely acceptable standard method with vast range of

applications and simultaneous analyses of many samples. Although the method has some

limitations as it is unsuitable for determination of solids in some heat sensitive liable samples

and time consuming.

2.2.1. Precision.

The Stillage Samples (Wheat and Lignocellulose) were run in triplicates to attain for accuracy

and negligible deviation.

Data Computations and analyses are referenced in the appendix section.

The % TS result from the laboratory procedures and that determined by the AKo Lab were

reported in the appendix.

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The % TS is reported to two decimal places, samples were analyzed in triplicates with

average report of replicate samples analyzed.

2.3. Standard Determination of Volatile Solids Content (VS %) of Stillage Samples.

Sample solids lost upon ignition at firing temperature of 550C (25C) are Volatile Solids.

Analysis of Volatile solids in a sample has important application in that it gives rough

estimation of the amount of organic matter present in the industrial wastes and effluents, solid

fraction of wastewater and activated sludge.

Muffle Furnace Analytical Procedure of Volatile Solids Analysis of Stillage Samples.

a). After determining the final weight in total solids analysis, the respective cooled oven driedStillage samples and crucible were placed in a muffle furnace and ignited at 550C at a 25C

for exactly 1hr.

b). Following the ignition duration for complete combustion process to take place, the oven

ignition switch is switched off and allowed to cool down for 10 minutes.

c). The cooled muffle furnace dried samples were then placed and kept in desiccator for an

hour. Immediately after samples were allowed to desiccate, samples were weighed together

with the crucible in the sensitive analytical measuring balance.

Cautions Taken.

Three replicates were analyzed for the Stillage samples (Wheat Stillage WS and

Lignocellulose Stillage LS) for reasonable statistical average measure. Comparable precision

with Total solids performed and Illustration of Data Computations on Volatile Solids analyses

obtained from laboratory procedure and from AKo Lab annexed in appendix section.

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2.4. Thermophilic and Mesophilic Anaerobic Digestion of Distillery Ethanol Waste-

Stillage for Methane Production.

2.4.1. Introduction.

A batch digestion procedure was employed with modifications of existing technique by

Angelidaki and Ahring (2004) for measuring the methane potential resulting from anaerobic

digestion of the Distillery Ethanol waste- Stillage (Wheat and Lignocellulose derived).

Triplicate reactors of Wheat Stillage and Lignocellulose Stillage of samples 2.73g and 5.20g

respectively, corresponding to 2%VS in the digester were incubated with 20ml of active

inoculum coming from full scale Thermophilic Biogas Plant (Sobacken-Bors) at 35C in

water bath shaker under Mesophilic anaerobic conditions and 55C under Thermophilic

anaerobic conditions over a 50-day digestion cycle. Reference material (Avicel) was used as

Control and water as blank instead of the substrates

The methane production was regularly monitored over the 50days digestion phase and the

concentration of methane was measured with gas chromatograph.

The inoculum for laboration was from full scale Thermophilic Biogas Plant (Sobacken-Bors)

for the thermophilic digestions as well as from a Mesophilic Plant (Gsslosa, Bors) for the

Mesophilic experiments.

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2.4.2 Materials and Supplies.

2.4.2.1. Equipments and Apparatus.

The below list of laboratory equipments and apparatus were used during the laboration.

50ml Measuring Cylinders and 50ml Beakers5ml Test tubes and 5ml MicropipettesGlass bottles of around 118ml with thick rubber septum- determination of volume of each

reactor done by weighing contained water in the glass bottles (reactors).

Temperature regulated and adjustable incubator for thermophilic digestion at 55C250l pressure lock glass syringe for fixed volume at exact pressure from reactors.Weighing balance (sensitivity measurement 100g-200g)Temperature-regulated Water bath shaker (35C) for Mesophilic anaerobic digestion.Gas Chromatograph thermal FID detector and methane standards.

2.4.3 Samples, Reagents and Supplies.

Gas Mixture of 20% CO2(g) and 80% N2(g)A Cellulose Avicel powder to be use for ReferenceCreamy liquid Wheat Stillage and black liquid Lignocellulose StillageActive Inoculum from thermophilic Biogas Plant, Sobacken-Bors and Mesophilic Biogas

Plant, Gsslosa-Bors.

The inoculum was stored at 55C with an anaerobic headspace in an incubator for 2days.

2.5. Method

Stillage distillery wastes collected from the Ethanol production plant of Norrkpping (Wheat

Based) and from the pilot plant Ethanol Plant (Lignocellulose Based) rnskldsviz -Sweden

were investigated. The effluent Stillage samples were stored in the cooling room.

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2.5.1. Laboratory Experimental Procedures.

The laboratory investigation procedure was performed as triplicate batch test runs for each

temperature digestion conditions, that is at Mesophilic (35C) or Thermophilic (55C).

Pure N2(g) gas could be used for flushing as alternative.

The triplicate reactors were then placed in the incubator at 35C or 55C. Occasionally during

incubation, the triplicate reactor batches were gently shaken and moved to readjust minor

temperature variation difference in the incubator. In case of Mesophilic digestion, the reactors

were placed in temperature regulated adjustable water bath at 35C .The water level in the

water bath shaker is consistently monitored and top up daily to facilitate optimalenvironmental incubation conditions for the digestion of the samples.

The procedure set-up was also experimented using blanks with only 20l inoculum and 5ml

distilled water to measure the amount of Methane yield from the inoculum. The quality of the

inoculum was also tested in addition using a triplicate of Reference Cellulose Avicel for each

run.

28.

During the stirring of the inoclum, three

reactors were picked at random and

placed into each Stillage samples: 2.73g

Wheat Stillage and 5.20g Lignocellulose

corresponding to 2% VS in the reactor

flasks. Stillage with total volume brought

to 5ml using distilled water.

Following the set up of the reactors

according to Fig.14, they were flushed

for 60-90 minutes with anaerobic gas

mixture of 20% CO2(g) and 80% N2(g) to

create an anaerobic environment reactors.

Fig 14. Illustrates the experimental set up of measurement for

Methane Potential yield under Mesophilic Anaerobic digestion

conditions and Thermophilic Anaerobic Digestion conditions for

respective Stillage samples; Wheat and Lignocellulose Stillage

over 50-day digestion phase. (Hansen et al. 2004)


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Placed on a magnetic stirrer at steady stirring revolution 20ml inoculum was transferred using

the measuring cylinder to each triplicate reactor. Three reactors were picked at random during

the inoculum stirring and added with each Stillage samples: 2.73g Wheat Stillage and 5.20g

Lignocellulose Stillage with total volume brought to 5ml using distilled water.

The reactors were flushed for 60-90 seconds with anaerobic gas mixture of 20% CO2(g) and

80% N2(g) to create an anaerobic environment in the headspace of the glass bottles (reactors)

following the set up. Refer to Fig.14 above for illustration of the experimental set up.

2.5.2. Experimental Consistency and Monitoring.

The methane levels in the headspace reactors were consistently and regularly measured

throughout the 50-day digestion phase. During the first week, daily measurements were taken,

followed by once a week afterwards measurements.

The methane samples about 250l were taken with a pressure lock syringe through the septum

from the headspace of the reactors. Following the syringes penetration into each reactors

headspace, was the pressure lock closure for possible sampling of fixed volume of methane

gas at exact pressure conditions in each reactor.

Measuring the Methane content in the samples before and after releasing the pressure from

the reactors, the produced volume of the methane can be calculated. The fixed volume of the

gas is taken by syringe withdrawal and directly injected into gas chromatograph for exact

measurement of the number of moles of the methane gas.

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30.

III. RESULTS


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3. RESULTS.

3.1 Data Analyses and Presentations.

The Results of the (TS %) and (VS %) annexed in the appendix section rounded up to two

decimal places. The samples were analyzed in triplicates with average values of triplicate

analyzed respective values reported.

3.1.1. Total Solids (TS) and Volatile Solids (VS) Computations on Stillage Samples.

Table 6 below illustrates the recorded respective weighing during the convection oven

procedure for the determination of Total Solids TS (%) of the Wheat Stillage (WS) and

Lignocellulose Stillage (LS). The Total Solids TS% for WS was analyzed to be 13.2% that is

0.132g/g while The TS% for the LS was analyzed to be 3.8% (0.0038g/g).

Samples

S/N

B

Predried Empty

Crucibles (g)

C

Evaporating Crucibles

+Samples

before drying at 105C

(g)

A

Evaporating Crucible

+ Samples after

drying at 105C (g)

Weight of dried

residue (g)

WS 1 46.99 74.78 50.73 3.74

WS 2 49.69 74.95 53.25 6.56

WS 3 47.61 71.89 50.76 3.15

LS 1 49.17 77.22 50.22 1.05

LS 2 49.73 81.65 50.94 1.21

LS 3 47.38 76.79 48.49 1.11

Table 6. Data obtained for determination of Total Solid TS (% g/g) of Stillage Samples.

A= weight of dried residue + crucible after drying at 105C, B= weight of Predried crucible

C=weight of Predried crucible + sample before drying

Thus TS (%) = {(A-B)/(C-B)}*100

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In Table 7 Illustrated below are the recorded representative sample (Wheat Stillage and

Lignocellulose Stillage) triplicate weightings during the 550C (25C) drying oven

procedure for the determination of Volatile Solids Table 7. VS g/g (%) of the Wheat Stillage

(WS) and Lignocellulose Stillage (LS).

Table 7.Volatile Solids %g/g analyses of Wheat Stillage and Lignocellulose Stillage

VS (%) = {(A-D)/(C-B)} * 100%

A=weight of dried residue + crucible after drying at 105C

B=weight of Predried dish

C=weight of Predried dish + sample before drying

D=weight of dried residue + dish after drying at 550C

32.

Samples

S/N

B

Predried

Empty

Crucibles

(g)

C

Evaporating

Crucibles

+Samples

before drying at

105C (g)

A

Evaporating

Crucible

+Dried

samples after

drying at

105C (g)

D

Evaporating

Crucibles

+Samples after

drying at 550C

(g)

Volatile Solids

Analysis 2%VS

sample

WS 1 46.99 74.78 27.79 48.12 0.094

WS 2 49.69 74.95 25.26 50.55 0.096

WS 3 47.61 71.89 24.28 48.38 0.098

LS 1 49.17 77.22 28.05 49.63 0.021

LS 2 49.73 81.65 31.92 50.40 0.017

LS 3 47.38 76.79 29.41 48.00 0.017


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3.2. Anaerobic Digestion of Ethanol Distillery Stillage Samples.

The data presentation and evaluation of triplicate batch reactors for each samples with

consecutive triplicate series for Wheat Stillage and Lignocellulose Stillage each which

resulting in a total of 12 reactors including cellulose controls, the control blanks (inoculum

and water only) and the Stillage Samples, each in triplicates was computed and analyzed

using MS Excel-sheet .

The amount of Methane produced was directly measured on the GC based on the volume of

the headspace of each triplicate reactors of each Stillage Samples. The CH4(g)-content per

0.25ml of reactor headspace was determined. For every measurements two readings from

each samples are taken and recorded before the pressure is released and after the pressure is

released to obtain the CH4(g) number of moles of each samples. For every measurement of the

Methane gas produced (nm, CH4(g)) at (T, Celsius (298K)= 22C) and Atmospheric

Pressure(Patm,= 101325 Pa), the volume of the methane produced is determined with reference

to the Peak Area standard methane mole number (nstd) the number of mole (n)of Methane gas

(nCH4) as deduced from GC analyses.

After running each samples readings of the Standard (100%) Methane is also determined.

Simply the methane gas yield is determined by measuring the concentration of before

pressure is released under experimental parameters of (T, Celsius (298K) = 22C) and

Atmospheric Pressure (Patm, = 101325 Pa) is:

Standard 100% Methane = n(std); n(std) = (pVm)/(RT)

Where (Atmospheric Standard Pressure): Patm, = 101325 Pa, (Sample Volume): Vm= 250 * 10-

9(m3), (Ideal Standard Gas Constant): R=8,314 and (Sampling Temperature) T= T, Celsius

(298K) = 22C.

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Thus, the number of mole of methane in the reactor can be deduced from the equation,

nstd = (A/Astd) X (nstd.93000/250), that is , n=(A/Astd)*nstd*372

where A= Area of each Stillage sample obtained from the GC curve

A(std) = Area of the standard methane (100%) analyzed

n(std) = number of moles of the standard methane (100%) analyzed

372 is derived from the ratio of the volume of the reactor by the volume of injected methane

It is important to note also that Vflask is the gas space in flask obtained by subtracting the

volume of the sampling mixture contents from the volume of the flask, which was 93ml.

Hence for the number of mole of Methane gas for each Sample is calculated and

n1a is the number of moles of methane produced before the release pressure in reactor

n1b is the number of moles of methane produced after release of pressure in the reactor

The Volume of the produced Methane however is obtained in between the respective

measurements before (na) and after (nb) release of pressure and can be derived by applying

the equation below, hence the produced methane in between and +1measurements was can

be calculated by

V(produced, m3) = ((na+1 - nb)*(R*T))/ Patm

The Volume of methane produced can be deduced using the mathematical formula above.

The Maximal produced Methane during the 50-day incubation digestion phase is referred to

as the Methane potential. The result of the amount of Methane content produced in sample

analyzed is thus the CH4 (g) produced per.

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3.2.1. Mesophilic Anaerobic Digestion of Ethanol Distillery Waste

Wheat Stillage.

WS

0,000

0,020

0,040

0,060

0,080

0,100

0,120

0,140

0,160

1st 2nd 3th 4th 5th 6th

Weeks

VolumeofBiogas(L)

Fig.15. Triplicate curve averages of Methane Potential yield from Wheat Stillage at 35C.

The above curve, illustrates recorded biogas production of Wheat Stillage analysis with slight

increase following the first week of Mesophilic digestion, later this proceeded to the second

up to the fourth week (the peak level of production) which was 0.140L the peak volume of

produced Biogas, after which the Methane produced then fairly dropped during the fifth week

and slight further decrease in the sixth, there was zero Methane production in the 7th week of

the laboratory analysis.

From Fig. 15 .curve it is however established that the peak Methane yield was

0.140L/0.5g VS that is, 140ml/ 0.5g VS CH4-content from the anaerobic digestion of Wheat

Stillage under 35C.

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3.2.2. Mesophilic Anaerobic Digestion of Stillage Samples

Lignocellulose Stillage

LS

0,000

0,050

0,100

0,150

0,200

0,250

0,300

0,350

0,400

0,450

0,500


Weeks

V

olumeofBiogas(L)

Fig.16.Triplicate average curve of Methane Potential yield from Lignocellulose Stillage 35C

There was marked obvious increase CH4 yield in the anaerobic digestion process at 35C

from the Lignocellulose Stillage, immediately after the 1st week of digestion with progressive

rise to 153ml/0.5g VS CH4 during the 2nd week continuous increase yield over the

consecutive weeks and slight decrease of the Methane gas after the fourth week and this

decrease was marked evident also between the 5th and 6th week of sampling during the 50day

digestion cycle at 35C Incubation.

The fourth week indicated the peak increase volume of Biogas Produced during the digestion

of Lignocellulose Stillage) under the mesophilic condition which can be referenced as0.436ml/0.5g VS CH4 from the anaerobic digestion of Wheat Stillage under 35C.

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3.2.3. Mesophilic Anaerobic Digestion of Stillage Samples

Comparison of Wheat Stillage and Lignocellulose Stillage.

WS vs LS

0,000

0,0500,100

0,150

0,200

0,250

0,300

0,350

0,400

0,450

0,500


Weeks

V

olumeofBiogas(L)

WS

LS

Fig.17. Methane Potential Triplicate Average comparison curves of LS & WS at 35C

Compared to Wheat Stillage peak CH4 yield of 138ml/0.5 VS, Lignocellulose Stillage

anaerobic digestion when subjected to 35C Mesophilic Condition demonstrated higher CH4

yield with maximum peak of 436ml/0.5g VS at the 4th week during 50-day anaerobic

incubation.

The Stillage samples however gave simultaneous increase in the CH4 yield shortly after the

first week of incubation and gave higher yield through the 2nd, 3rd and 4th week and with a

consistent fair decrease yield between the 5th and 6th week.

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3.3. Thermophilic Anaerobic Digestion of Stillage Samples.

Wheat Stillage.

WS

0,100

0,150

0,200

0,250

0,300

0,350

0,400

0,450

0,500

0,550

0,600


Weeks

V

olumeofBiogas(L)

Fig.18. Methane Potential Triplicate Average comparison curves of Wheat Stillage at 55C

Following the onset of observable yield of CH4 at 55C Thermophilic incubation in the 1st

week by the Wheat Stillage, 229ml CH4/ 0.5g VS was measured on the GC in the 2nd week,

while peak yield of 575ml CH4/0.5g VS was recorded in the 4th week and continuous gradual

decrease through the following digestion period.

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3.3.1. Thermophilic Anaerobic Digestion of Stillage Samples.

Lignocellulose Stillage

LS

0,000

0,020

0,040

0,060

0,080

0,100

0,120

0,140

0,160


Weeks

VolumeofBiogas(L)

Fig.19.Methane Potential Triplicate Average curves of Lignocellulose Stillage 55C.

In Fig.19, there was rapid production of CH4 following the 1st week of digestion from 150ml

CH4/0.5g VS of Lignocellulose Stillage to 280ml/0.5g VS after 14 days (2nd week) and

recorded rapid production of Methane after the second week at 55C thermophilic standard

condition followed by observable minute constant production rate over the following

remaining days of 50-days digestion phase.

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3.3.2. Thermophilic Anaerobic Digestion of Stillage Samples

Comparison of Wheat Stillage and Lignocellulose Stillage.

WS vs LS

0,000

0,100

0,200

0,300

0,400

0,500

0,600

0,700


Weeks

V

olumeofBiogas(L)

WS

LS

Fig.20. Methane Potential Triplicate Average Comparison curves of LS & WS at 55C

The Lignocellulose Stillage demonstrated higher digestibility compared to the Wheat Stillage.

This however can be referenced to the curves above with more methane produced by the

Wheat Stillage of about 575ml/0.5g VS in contrast to 145ml/0.5g VS by Lignocellulose

Stillage during the peak period of digestion; that is the 4 th week.

However in both Stillage Samples there was marked progressive increase in production of

CH4 evident from the 2nd week onwards and significant increase rate over the 3rd and 4th

weeks and decrease yield of CH4 towards the completion of the thermophilic anaerobic

digestion condition at 55C.

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3.3.3. Comparisons of the Temperature Anaerobic Digestion Conditions on

Stillage Samples (Wheat Stillage and Lignocellulose Stillage), Reference

Cellulose Controls and Blanks.

Thermophilic Digestion 55C Mesophilic Digestion 35C

0,000

0,100

0,200

0,300

0,400

0,500

0,600

0,700


Weeks

Vo

lum

e

ofBiogas

(L)

WS

LS

Rf

CS

0,000

0,0500,100

0,150

0,200

0,250

0,300

0,350

0,400

0,450

0,500


Weeks

V

olume

ofBiogas(L)

WS

LS

Rf

CS

Fig. 21A shows triplicate average CH4 yield

curves analyzed and measured for batch

reactors at 55CThermophilic digestionon

each Stillage samples (WS & LS), the

Reference Cellulose Avicel controls and the

control blanks containing only inoculum and

water. There was steady successive yield of

CH4 for each curves with peak value of CH4

yield of the Wheat Stillage (WS) noticeable

on the 4th week of digestion of about 575ml

CH4 / 0.5g VS, 145ml CH4 / 0.5g VS from

the Lignocellulose Stillage (LS). The

Reference Cellulose Avicel also showed

maximal degradation of 187ml CH4/0.5g VS

during 4th week. The Control Sample of

inoculum and water only also proved to

minimal CH4 digestibility yield of 116ml

CH4/ 0.5g VS

During Mesophilic 50-day digestion as

measured with GC, the Fig 21B above depicted

the CH4

yield average curves GC analyzed for

respective Stillage (WS & LS), the Blank

Controls with (water and inoculum only) and

the Reference Cellulose Avicel Controls.

Unlike the 55Cdigestion, at 35C the peak

CH4 measured was 380ml WS/ 0.5g VS

following 28 days of incubation (4th week),

while Lignocellulose Stillage proved a

digestion potential rate with yield of 436ml

CH4/ 0.5g VS at the 4th week .The Reference

Cellulose Avicel Controls degradation likewise

resulted to higher yield of 104ml CH4/ 0.5g

VS compared to Thermophilic digestion

conditions of 187ml CH4/ 0.5g VS in 4th week

with negligible minimum yield in the Control

Samples of 130 CH4/ 0.5g VS during the 4th

week

41.

Fig.21B. Methane Triplicate Average Curve forrespective samples at 35C (Mesophilic Digestion)

Fig.21 A. Methane Triplicate Average Curve for respectivesamples at 55C (Thermophilic Digestion)


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42.

IV. DISCUSSIONS & CONCLUSIONS


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DISCUSSIONS AND CONCLUSIONS

The CH4 Potential analysis gave same yield value for Wheat Stillage and Lignocellulose

Stillage as 0.473 m3CH4/kg VS and 0.407 m3CH4/kg VS respectively.

The Total Fat (TF) Content of the Wheat Stillage was much higher having value of 73.8g/kg

VS while Lignocellulose Stillage was zero. The Total Nitrogen Content (TN) of the

Lignocellulose Stillage of about 4.7g/kg TS was on the other hand much less compared than

the Total Nitrogen Content(TN) of the Wheat Stillage which is 63.8 g/kg TS. The Protein

Contents of the Wheat Stillage analyzed were significantly much higher in amount having the

values of 389.3g/kg TS Protein Content while the Carbohydrate content was much lower

463.1g/kg TS Carbohydrate Content relative to 416.7g/kg TS Carbohydrate of Lignocellulose

Stillage.

The Ammonium content of the Wheat Stillage is 1.46g/ kg TS about twice more than that of

the Lignocellulose Stillage with 0.7g/kg TS Ammonium content.

The above analyses however reflect the fact that the decline Methane CH4 production by

Wheat Stillage could be likely subjected to the higher Protein values which might have been

inhibited by ammonia. This however is in contrast to the elevated production of Methane gas

by the Lignocellulose Stillage with lower Protein Content although there could be some other

inhibitors that might likely be present with negligible inhibitory effects.

The decreased methane production by the Wheat Stillage unlike Lignocellulose Stillage can

be accounted with reference high amount of 73.8g/kgTS Fat Content with associated probable

effects of long chain fatty acids during degradation process conditions.

In addition, negative methane potential yields observed might be suggested to be presence of

inhibitory substances likely to be present in both Wheat Stillage and Lignocellulose Stillage

samples resulting in lower methane which can be attributed to the high protein content of the

Wheat Stillage with resultant ammonium inhibitory effects and other probable inhibitors in

the Lignocellulose compared to yields from the control batches with inoculum and water only.

It is essential to investigate further experimentally in future studies, the possible inhibitory

sources associated with the Stillage Samples to obtain increased CH4 potential result.

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Potential promising recommendations in attaining extensive research findings in determining

the associated inhibitory effects for negative CH4 produced center on possible cost effective

pretreatment methods, Enzymatic Upgrading, Co-digestion with other Organic Waste

Streams.

Biogas future as a renewable alternative fuel depends to some extent on how western

countries and other developing nations address the enormous challenge of controlling

greenhouse gases and atmospheric emissions of carbon dioxide. In addition, another

important factor of production of Biogas from Ethanol Distillery Waste depends relatively on

improved production technology for Ethanol from economically cost affordable cellulose-

based Feedstocks.

The Concept of Stillage Utilization for Biogas Production offers effective Waste Management

and Resource Development solutions with positive measures for the economy, improved air

quality and sustained energy security, the crucial necessary however revolves round is a clear

vision and strong collaborative partnership among the various stakeholders.

The AK Lab analytical experimental result (ref. Table 10) presented the potential methane

analysis of each respective Stillage, that is, Wheat Stillage and Lignocellulose Stillage have

gas potential CH4(g) yield of 0.4m3CH4/kgVS with the CH4(g) constituting with the 70% CH4content of the produced Biogas. Hence the method will be very viable but will have to be tried

on a pilot scale so the necessary modification made for a commercial system.

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45.

VI. REFERENCES.


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References.

Angelidaki, I., Ahring, B.K., (1992). Effects of free long-chain fatty acids on thermophilic

anaerobic digestion. Applied Microbiology and Biotechnology 37, 808-812.

Bouallagui, H.; Touhami, Y.; Ben Cheikh, R.; Hamdi, M. (2005) Bioreactor performance inanaerobic digestion of fruit and vegetable wastes. Process Biochemistry 40(3-4): pp 989-999.

Biofuel Review Magazine, December 2006.

Biogas Upgrading and Utilization, IEA Bioenergy (International Energy Agency) (2004).Biofuels for transport: an international perspective. International Energy Agency, OECD

Christoph Berg., (2004). WORLDFUEL ETHANOL ANALYSIS AND OUTLOOK

Danish Biogas Co-digestion for Energy and Environment, Washington, D.C., (2006).

EurObservER (2006). European Commission on Energy Publications (EUROPA)http://ec.europa.eu/energy/res/publications/barometers_en.htm.

Farrell et al. (2006)Ethanol can contribute to energy and environmental goals. Science 311,p.506508.

F.O. Licht, (2004).World Ethanol & Biofuels Report, V2 N. 19.

F.O. Licht., (2005): cited in Renewable Fuels Association,Homegrown for the Homeland:

Industry Outlook 2005, Washington, DC: p. 14

Focus Bioenergy (2003). A REVIEW, Swedish Bioenergy Association. www.svebio.se

Hagen. et al., (2001).Adding gas from biomass to the gas grid, SGC report 118.

Hansen, T.L, Schmidt, J.E., Angelidaki, I., Marca, E., Jansen, J.C., Mosbaek, H., et al. (2004).Method for determination of Methane potential of solid waste. Waste Management and

Research, 24:393-400.

Holm J B (2000), The future of biogas in Europe, a general overview.

Hsu, T, (1996). Pretreatment of Biomass in Handbook in Ethanol: Production andUtilization; pp 179-212.

Josephine Bahr, (2006). SwedishEnergy agency Presentation of Bioenergy in Sweden.Seminar of -biogas in Sacramento. Published by SWENTEC, Swedish EnvironmentalTechnology Council.

Kiely, G.; Tayfur, G.; Dolan, C.; Tanji, K (1997). Physical and Mathematical modeling of -Anaerobic Digestion of Organic Wastes. Water Research 31 (3): 534-540.

46.


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Licht FO., (2004).Ethanol production costs: a worldwide survey. Agra Informa Ltd, Kent,United Kingdom http://www.agra-net.com.

Microslav Hutnnan, Marek Honak, Vladimir Havaklar (2005). Proceedings of the 30thInternational Conference of SSCHE, Department of Environmental Engineering, Faculty of

Chemical and Food Technology, Slovak University of Technology.

M. Persson., (2003).Evaluation of Swedish plants for upgrading of biogas, SGC-report 142

Mosier, N. et al. (2005) Features of promising technologies for pretreatment oflignocellulosic biomass. Bioresour. Technol. 96,19861993

O. Jnsson, 2001. The Swedish Case for Methane Gas, ENGVA Annual Meeting, Malm.

Ogier, J.C. et al. (1999) Ethanol production from lignocellulosic biomass. Oil Gas Sci-Technol 54, 6794.

Renewable Fuels Association RFA (2005). World Ethanol Production Outlook.

Saha, N.K.; Balakrishnan, M.; Batra, V.S. (2005). Improving Industrial Water Use: CaseStudy for an Indian distillery. Resour. Conserv.Recycl.43, 163-174.

Samir Kumar Khanal, Scott Schaefer, Shihwu Sung (2005):Anaerobic Digestion of ThinStillage to produce Methane and Class-A Biosolids. Biotechnology Byproducts Consortium,Iowa University.

Shell and Codex Exploration of Biofuels (2006): The Biofuel Review Magazine.

Stewart, D.J.; Bogue, M.J.; Badger, D.M. (1984). Biogas production from crops and organicwastes New Zealand Journal of Science 27(3): 285-294.

Solagro, (2001). Sweden from Biogas to Energy, an European Overview.

Viswanath et al., (1992).Integration of Anaerobic Digestion in biomass by-product & wasterecovery

Von Sivers, M. and Zacchi, G. (1996) Ethanol from lignocellulosics: A review of theeconomy. Bioresour. Technol. 56, 131140

Weiland, P. (1993). One- and Two-Step Anaerobic Digestion of Solid AgroindustrialResidues Water Science &Technology 27(2): 145-151.

Wyman, C.E. et al. (2005) Coordinated development of leading biomass pretreatmenttechnologies. Bioresour. Technol. 96, 19591966

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48.

V. APPENDICES


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APPENDIX I. DATA FIGURES & TABLES OF RESULTS.

The Table 6 below gives the recorded average values of the Total Solid Contents of therespective Stillage samples

Samples

S/N

B

Predried Empty

Crucibles (g)

C

Evaporating Crucibles

+Samples

before drying at 105C (g)

A

Evaporating Crucible +

Samples after drying at

105C (g)

Weight of dried

residue

WS 1 46.99 74.78 50.73 3.74

WS 2 49.69 74.95 53.25 6.56

WS 3 47.61 71.89 50.76 3.15

LS 1 49.17 77.22 50.22 1.05

LS 2 49.73 81.65 50.94 1.21

LS 3 47.38 76.79 48.49 1.11

Table 6. Data obtained for determination of Total Solid TS (% g/g) of Stillage Samples.% Total Solids = (Weight dry crucible + dry Stillage sample Weight dry Stillage sample) X 100

Weight Stillage sample

Table.7 below illustrates the analytical experimental average values of the Volatile Solid

Table 7.Volatile Solids %g/g analyses of Wheat Stillage and Lignocellulose Stillage.

% Volatile Solids = (weight ofdry sample+ crucible at 105C-wieght ofcrucible + dried sample at 550C) X 100%

Weight of Stillage sample49.

Samples

S/N

B

Predried

Empty

Crucibles (g)

C

Evaporating

Crucibles +Samples

before drying at

105C (g)

A

Evaporating

Crucible

+Dried samples

after drying at

105C (g)

D

Evaporating

Crucibles

+Samples after

drying at 550C (g)

Volatile Solids Analysis

2%VS sample

WS 1 46.99 74.78 27.79 48.12 0.094

WS 2 49.69 74.95 25.26 50.55 0.096

WS 3 47.61 71.89 24.28 48.38 0.098

LS 1 49.17 77.22 28.05 49.63 0.021

LS 2 49.73 81.65 31.92 50.40 0.017

LS 3 47.38 76.79 29.41 48.00 0.017


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CUMULATIVE AVERAGES OF METHANE VOLUME OF RESPECTIVE ANALYSED SAMPLES: (WHEAT

STILLAGE WS, LIGNOCELLULOSE STILLAGE LS, REFERENCE Rf & CONTROLS (WATER).

The table below shows the average volume of methane CH4 produced in each sample under

thermophilic conditions through 50 days digestion. There was no methane produced in all theanalyzed samples (Wheat Stillage, Lignocellulose Stillage, Reference Avicel and ControlBlanks) on the 7th week of digestion.

Table 8. Thermophilic Anaerobic Digestion Volume of CH4(g) (L) of respective WheatStillage WS, Lignocellulose Stillage LS, Control CS & Reference Rf.

Illustration in Table 9 below shows computed averages Volume (L) of CH4 during theMesophilic anaerobic digestion of each analyzed samples below over 50day period and at

35C. Similarly no methane content was recorded on the 7

th

week of the analysis underMesophilic conditions

Table 9. Mesophilic Anaerobic Digestion Volume of CH4(g) (L) of respective Wheat Stillage

WS, Lignocellulose Stillage LS, Control CS & Reference Rf.

50.

Weeks

1st 2nd 3rd 4th 5th 6th

WS 0,032 0,229 0,539 0,575 0,603 0,337

LS 0,015 0,028 0,125 0,145 0,145 0,121

Rf 0,018 0,187 0,187 0,187 0,187 0,167

CS 0,011 0,038 0,095 0,116 0,116 0,089

Weeks


WS 0,006 0,017 0,024 0,138 0,135 0,135

LS 0,000 0,153 0,279 0,436 0,437 0,434

Rf 0,000 0,084 0,092 0,104 0,098 0,065

CS 0,000 0,003 0,010 0,013 0,012 0,010

Samples

Samples


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CH4 pot

2007-04-18 enhet

Drank 1

(vete)

Drank 2

(lignocell)

TS % 15% 3,6%

VS % av TS 93% 44%

ton VS/ton 0,14 0,02

N tot g/kg TS 63,8 4,7

Fetter g/kg TS 73,8 0,0

Proteiner g/kg TS 389,3 24,7

Kolhydrater g/kg TS 463,1 416,7

NH4 g/kg TS 1,46 0,7

C/N 10 66

COD-Cr mg/kg prov 170 62

total CH4 pot

(m3/kgVS)

P tot g/kg TS CH4m3/ton

S

pH

Na

K g/kg TS

Mg g/kg TS

Ca

Grnsvrde Eco-labelmg/kg TS

1 Cd mg/kg TS

100 Cr mg/kg TS

1 Hg mg/kg TS

50 Ni

mg/kg TS

Table 10.Laboratory Analysis of Wheat and Lignocellulose Stillage Composition.

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100 Pb mg/kg TS

300 Zn mg/kg TS

100 Cu mg/kg TS

Energivrde kcal/100g 62,3 6,51

Energivrde kJ/100g 261 27,2

Energivrdeper kg TS kJ/100g 17 517 7 556

Energivrdeper kg VS kJ/100g 18 913 17 000

Tot N g/kg 9,5 0,2

%N av TS 6,4 0,5

Gaspotentialm3 CH4/kgVS 0,4 0,4

m3 CH4/ton 55,2 6,4

%CH4 70% 70%

m3 gas/ton 78,9 9,1

0,85m3/ kgVS fett0,50 m3/kgVS prot

0,40m3/

kgVSkolhydr

Drank 1 (vete)Drank 2(lignocell)

Drank 1

vete)Drank 2(lignocell)

Drank 1(vete)

Drank 2(lignocell)

0,068 0

0,206 0,028

0,473 0,407

65,9835 6,44688

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Table 11. World Leading Ethanol (Million Liters) Producing Countries.

Country 2004 2003

1. Brazil 15338 14428

2. USA 13950 10900

3. China 3650 3400

4. India 2000 190

5. France 830 817

6. Russia 760 745

7. Spain 420 304

8. South Africa 409 404

9. UK 400 410

10. Saudi Arabia 340 350

11. Ukraine 290 284

12. Thailand 280 250

13. Germany 270 280

14. Canada 245 204

15. Italy 210 240

SOURCE: F.O. LICHT, WORLD ETHANOL & BIOFUELS REPORT, V2 N. 19 JUNE 6, 2004.

World Ethanol Production

2003 & 2004

0

20004000

6000

8000

10000

12000

14000

16000

18000

1.Br

azil

3.China

5.Fr

ance

7.Sp

ain9.

UK

11.Ukr

aine

13.Germany

15.Ital

y

Ethanol Leading Producing Countries

VolumeofEthanol

Produced(MillionLiters

Ethanol Production Year 2004

Ethanol Production Year 2003

anaerobic digestion thesis

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